1. Field of the Invention
The present invention relates generally to a communications network system organized of a plurality of interconnected networks, and more particularly to an internetworking apparatus for interconnecting a plurality of networks, which is generally referred to as a router, a bridge or a bridging router.
2. Description of the Related Art
Conventionally, an internetworking apparatus or node for interconnecting a plurality of networks is configured such that processors for performing packet forwarding processing are disposed corresponding to interfaces of the respective networks and are coupled to each other through a bus. Techniques described in U.S. Pat. No. 5,434,863 may be taken as an example of such an internetworking node.
FIG. 2 schematically illustrates an example of a communications network system comprising a plurality of interconnected networks. In the illustrated system, seven CSMA/CD (Carrier Sense Multiple Access with Collision Detection) networks 5-11 are connected through three routers 12-14 which support Internet Protocol (IP) as a protocol for network layer. In the router 12 in the prior art example, when a packet is forwarded from a network 5 to a network 8, a processor in the router 12 disposed corresponding to an interface of the network 5 and a processor in the router 12 disposed corresponding to an interface of the network 8 respectively execute predetermined fixed amounts of assigned processing for forwarding the packet therebetween.
Further, in the illustrated prior art example, even when the forwarding of a packet from the network 5 to the network 8 and the forwarding of a packet from a network 6 to a network 7 are simultaneously carried out through the router 12 in the communications network system, a plurality of packets can be simultaneously forwarded by processors disposed corresponding to interfaces of the networks 5-8 in the router 12.
The above-mentioned prior art system, however, has the following problem.
For example, if packets to be forwarded from the networks 5-7 to the network 8 concentrate in the router 12 in the communications network system illustrated in FIG. 2, the processor disposed corresponding to the interface of the network 8 must process all packets transmitted thereto from the processors disposed corresponding to the interfaces of the networks 5-7, thereby resulting in unbalanced processing loads on the respective processors. Eventually, when the processor disposed corresponding to the interface of the network 8 is burdened with a processing load exceeding its processing capability, the packet forwarding capability of the entire system is determined by the processing capability of the processor disposed corresponding to the interface of the network 8. Since the respective processors forward packets by executing predetermined fixed amounts of their respective assigned processing even in such a case, processing load cannot be distributed among the respective processors to improve the processing capability as the entire system.